Pasture is a more-rewarding environment for dairy cows than full-time housing, researchers at Queen’s University Belfast have concluded.
The behaviour of 29 Holstein-Friesian cows was studied in trials carried out at the Agri-Food and Biosciences Institute, Belfast.
The cows had all been at pasture and were then housed in cubicles for eight weeks. They were trained to approach a bucket containing concentrate feed at one location and not to approach an empty bucket at another.
The cows were then divided into two groups with a similar range of ages, time from calving and incidence of lameness. Each group had 18 days of overnight pasture access and 18 days of full-time indoor housing.
During this time, the cows were presented with three further empty buckets, spaced between the first two, to test their optimism or pessimism, or judgement bias.
Cows that approached these middle buckets could be described as having a “glass half-full” emotional state.
Results showed that, when the cows were at pasture, they were less likely to approach the bucket they knew contained feed, and took longer to do, compared to when they were housed.
However, the cows did not approach the middle buckets faster than when they were housed full-time.
“We found no treatment differences towards the middle buckets, suggesting there was no difference in judgement bias,” says Andrew Crump, postdoctoral researcher from the university’s school of biological sciences and lead author of the scientific paper.
Mr Crump suggests that maybe cows don’t have judgement biases, or that the research methodology was not sensitive enough to detect them.
The researchers suggest that the longer response times of the cows at pasture shows they have more rewarding lives and better welfare.
This is supported by that fact that they had fewer, longer, lying bouts and more synchronous lying behaviour.“The results suggest that reward valuation was a more-likely explanation,” says Mr Crump.
The possibility that cows at pasture could have been less motivated to eat because they began grazing at dawn, while the housed cows were only offered fresh silage at 9am, was discounted because the effect would have been strongest early in the day and decreased as all cows spent longer with their equivalent rations, and time of day did not affect speed of response.
There was also no relationship between response time and body condition – which was scored during both phases of the experiment.
Worldwide, most milk now comes from dairy cows without any access to pasture, according to the researchers. But more than 95% of British and Irish dairy cows went out to pasture in 2019, and Finland, Norway and Sweden have banned full-time housing.
The research has been published in the Nature journal Scientific Reports.